This application claims the priority of German Application No. 199 22 338.6, filed May 14, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method for establishing a defined active relationship between the operation of the accelerator pedal and the resulting braking torque of a vehicle.
The driving power of today""s vehicles is normally controlled by means of the accelerator pedal. When the accelerator pedal is continuously operated starting from the zero position, the drive torque of the engine (in the form of an internal combustion engine) is correspondingly continuously increased in that the control element responsible for the drive, such as the throttle valve in the case of Otto engines, is controlled. In the zero position itself of the accelerator pedal, no drive torque is transmitted; that is, the engine changes into the coasting operation, whereby a so-called engine drag torque is caused.
FIG. 4 illustrates a possible accelerator pedal characteristic according to the current state of production. In this connection, FIG. 4 shows a characteristic drive torque curve 1, which is obtained in the case of a low engaged gear, and a characteristic drive torque curve 2, which occurs when a high gear is engaged, as a function of the accelerator pedal angle W (abscissa) . The accelerator pedal angle W may, for example, have an adjusting range of 0xc2x0 to 18xc2x0. The drive torque is entered on the ordinate in FIG. 4, the decelerating torque Mv, (braking torque, negative drive torque) being illustrated below the zero line and the accelerating torque MB (positive drive torque) being illustrated above the zero line. In the zero position of the accelerator pedal, that is, Wxe2x89xa60xc2x0, different braking torques occur automatically and abruptly, particularly as a function of the engaged gear and of the engine drag torque: Mv=M1 for the characteristic drive torque curve 1, and Mv=M2 for the characteristic drive torque curve 2; that is, the braking torque M1 in the low gear is considerably larger than the braking torque M2 in the high gear.
In the case of this type of drive control, the driver has no influence by way of the accelerator pedal on the deceleration occurring in the zero position. It occurs automatically from the momentarily existing drag torque of the engine (such as an Otto engine or a Diesel engine). The drag torque, in turn, is also a function of a plurality of factors, as, for example, of the rotational engine speed, of the vehicle speed, of the engaged gear, of the displacement and/or of the transmission type (for example, a manual transmission or an automatic transmission).
FIG. 5 schematically shows the resulting drive torques (or braking torques) in the form of acceleration a (or deceleration) as a function of the respective engaged gear and of the momentary vehicle speed v in the case of a vehicle having a manual transmission according to the state of the art.
In particular, the higher the vehicle deceleration when the accelerator pedal is released, the easier it is to drive in a line of vehicles. This deceleration is composed of the inherent deceleration (aerodynamic drag, rolling resistance) and of the deceleration resulting from the engine drag torque.
Although the use of low gear positions and high rotational speeds makes driving in a line of vehicles easier and more comfortable, it represents the opposite of a low-consumption driving method and is also connected with noise emissions and engine wear. A driver who is concerned about consumption will use a high gear, if possible. Particularly when driving in a line, a high gear and thus a low drag torque is a disadvantage because, for the adaptation of one""s own vehicle speed to the speed of the vehicle driving ahead, frequent braking must take place which reduces comfort. In order to avoid such braking, the driver often allows his own vehicle to roll closer to the vehicle driving ahead than a safe distance would allow.
It is an object of the invention to improve an accelerator pedal characteristic of the above-mentioned type such that the above-mentioned disadvantages are avoided. Particularly, comfort, safety and fuel consumption of the vehicle are to be improved.
The simplifying term xe2x80x9caccelerator pedal characteristicxe2x80x9d is a method by which a defined active relationship between the operation of the accelerator pedal and the resulting drive torque or braking torque of the vehicle is established.
With respect to a method for establishing a defined active relationship between the operation of the accelerator pedal and the resulting braking torque of a vehicle, according to the invention, the possible adjusting range of the accelerator pedal is divided into at least two control ranges. In the first control range below a first defined accelerator pedal angle, control elements, which can cause a deceleration of the vehicle, are controlled corresponding to a defined braking torque course.
In principle, in a second control range above a second accelerator pedal angle, which may be equal to the first accelerator pedal angle or larger than the first accelerator pedal angle, the engine torque and/or the drive torque is controlled in the customary manner. However, this second control range itself is not the object of the invention.
In a further development of the invention, in a third control range between the first and the second defined accelerator pedal angles, the control elements, which can cause a deceleration and an acceleration, are controlled such that the braking torque or the drive torque of the vehicle is held constant at the value which exists when an accelerator pedal angle is reached in the third control range. In this case, the invention is based on the fact that a range is assigned to the driver in which he desires neither a drive nor a deceleration, and which is not defined to be so small that a back and forth swinging can take place between the drive and the deceleration.
The invention is ideal in combination with control elements (16, see FIG. 6) of systems that can influence the drag torque of the engine in a targeted manner. In the first control range, when the first defined accelerator pedal angle mentioned above is reached, or in the third control range, when the second defined accelerator angle mentioned above is reached, for example, the drag torque is reduced as far as possible in order to utilize the kinematic energy of the vehicle as long as possible. When the accelerator pedal is moved in the deceleration direction, that is, in the case of a further decrease of the accelerator pedal angle below the first defined accelerator pedal angle, the drag torque is increased continuously. Control elements 16, which permit such a drag torque control, are, for example, electrically controllable valves of EVT systems (EVT=electrically variable valve gear) , in the case of which the valves can be arbitrarily closed, or control elements of a crankshaft starter generator (KSG).
Additional control elements 16 which can cause a deceleration of the vehicle are, in connection with the accelerator pedal characteristic according to the invention, for example, components of wheel brake control systems for active braking interventions independent of the operation of the brake pedal or components of electronically controlled automatic transmissions for an automating backshifting of the gears.
By means of the present invention, a plurality of advantages are achieved. Thus, for example, in the case of automatic vehicles, considerable comfort is gained in that, in the case of a driving in a queue, a change must not constantly take place between the accelerator pedal and the brake pedal. Safety is gained by maintaining a safe distance without experiencing fatigue. Nevertheless, in the case of manual transmission vehicles, a fuel-saving method of operation is permitted as the result of low rotational speeds and high gears. In conjunction with energy recuperation systems (for example, the crankshaft starter generator (KSG)), a considerable amount of fuel can be saved. A comfortable driving method, which does not require habituation and presents no problems, is achieved in connection with an engine stop, automatic clutches, one-way clutches and CVT transmissions.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.